The present invention relates to a reference oscillator controlling device in a very small aperture terminal (VSAT), and more particularly to a reference oscillator controlling device in a VSAT which makes a relatively unstable reference oscillator a precise reference oscillator by synchronizing a reference oscillator of the VSAT with a clock extracted from a data stream which is generated by a precise reference oscillator in a host station of a VSAT.
Generally, a VSAT transmits data in a burst manner via satellite to a host station, and to receive the data of a burst manner in the host station, the transmission frequency from the local station must be exactly stable. For the stable frequency in the local station, an oscillator having a high stability is required, and so, a stable and precise reference oscillator of high price is currently used in the local station. However, there remains a burden of the cost in establishing a VSAT due to the high price of such a precise reference oscillator.
On the other hand, one of the techniques for controlling a reference oscillation frequency in a communication system between a host station and local station, such as the VSAT system, is disclosed in U.S. Pat. No. 5,271,039. The disclosed technique is about a local oscillating portion and BPSK demodulating portion for making a local oscillation frequency stable during the modulation/demodulation for sending/receiving, and the stability of the frequency is achieved by generating phase difference information through a controller and generating a symbol clock through an A/D converter and a DSP by an IF.
Thus, the above technique is employed for maintaining a stable frequency by the feedback of the phase difference information of a control circuit as a local oscillation control signal, and for simplifying the structure of a circuit. Accordingly, the technique cannot be applied to actuate an unstable reference oscillator with precision.